Thursday, February 28, 2013

Siberia: Nearly 105 years between giant space rock collisions!

Keeping up with the times as always, I've only recently heard about the February 15 meteor impact near Chelyabinsk, and have, today, finally dragged myself to the internet to see all the dash-cam videos.
` Installed for the purpose of recording events in cases of police corruption or insurance scammers, dashboard cameras have provided many angles of viewing the 7,000-ton meteor as it flared up in the earth's atmosphere. (Hooray for legal fraudsters?)

As it approached the earth, the meteorite was only 50 feet in diameter when it exploded into an enormous fireball (sometimes called a bolide), with the strength of a large nuclear warhead at 500 kilotons. Luckily for the folks below, this happened so high in altitude that the air was too thin to conduct much of this force.
` The infrasound from the shockwaves were detected by a global network of monitoring stations dedicated to use for upholding the Comprehensive Nuclear Test Ban Treaty. (These same stations also detected North Korea's third nuclear test on February 12, finding it to be laughably small in comparison to the meteorite, although that Kim Jong young-un would probably claim otherwise.)

There are, of course, many videos of said shockwaves, blowing out windows and sending glass and debris flying. In this case, stationary security cameras were more instrumental in getting these shots, as well as folks who have whipped out their video cameras in response to the meteor.

From this, some 1,500 people were reported injured (mostly from glass), and to add insult, many homes were missing windows or otherwise damaged during the winter in Siberia! (And here I was thinking that single-pane aluminum windows are bad!)

Not only is this the second well-documented impact of an enormous meteor recorded in science history, but it is also the second such meteor impact recorded in Siberia. (Thus, without Siberia, none of this could have happened...)
` The odds of two huge meteors striking Siberia really aren't so low, considering that its borders stretch to nearly 10% of the earth's land surface, and the fact that the two impact sites are about three thousand miles apart.

More interesting (to me) is learning that there have been other large meteor impacts at times between 1908 and 2013, which I've never heard of before. However, I am getting ahead of myself...

The first of these Siberian meteors was none other than the object that exploded six miles above Tunguska in 1908, flattening millions of trees in a butterfly-shaped pattern, although leaving stripped trunks standing directly under the impact point.
` An unknown number of people were killed, along with thousands of reindeer and other wildlife, in a fireball, which was then extinguished by a powerful shockwave. In Britain, the night sky was so bright that people reported being able to read by its light -- this was caused by sunlight reflecting off the fallout from the blast.

I remember reading somewhere that there were native Tunguskans who had thought the explosion came from the thunder god Agdy. Scientists who have judged the power and height of the explosion, however, think the most likely candidate is a crumb of rock some fifty feet across, or perhaps even a dense piece of comet.
` Even more than the nuclear warhead-like explosions is the fact that nowadays meteors can be mistaken for such weapons. In fact, Carl Sagan mentioned this possibility in the much-beloved 1980 science program, Cosmos, just after describing the Tunguska event:

"It's a strange scenario, a small comet hits the earth, as millions of them have during the history of our planet, and the response of our civilization is promptly to self-destruct. Maybe it's unlikely..."

But, as I found, this scenario is not all that far-fetched from actual history. There apparently have been other sizeable meteorites to hit the earth in recent times, such as the "Brazillian Tunguska" that caused a disastrous forest fire in 1930. If it had hit a large city instead of a rainforest, the course of World War II may have been very different.
` In 1996, U.S. military satellites detected a 100-megaton explosion over Greenland, safely away from war zones, and later, a 12-kiloton explosion over the Mediterranean Sea. This was in June of 2002, and if the meteor had struck the earth earlier, it could have hit India or Pakistan, both countries from which nuclear threats had been coming.
` Worse, the military of either country would have had no way to tell what the explosion had been from and so presumably would have started looking for someone to blame.

With all the meteor-tracking that goes on in the world, I wondered, how do we miss these ones that hit us? According to a Nature News article by Geoff Brumfiel, an asteroid called 2012 DA14 was expected to come within about 17,200 miles of the earth on the day of the Chelyabinsk impact, which is 5,000 miles within the orbit of geosynchronous satellites.
` The European Space Agency's space debris office and the Minor Planet Center in Massachusetts hadn't detected the rock that actually hit the earth, mostly because it is several times smaller than 2012 DA14 and not nearly as noticeable. (There are also some videos of 2012 DA14 as it passes by, safely at a distance.)

So, even though these smaller objects are as dangerous as nuclear weapons, we still have no way of telling whether or not they're coming and have no system in place to prevent them from destroying cities and such. On my latest foray onto GooglePlus, I noticed that Penny4NASA had something to say about this state of affairs:
We are at a pivotal point in human history, when we finally have the ability to avoid our own extinction from a catastrophic impact. Given our long history of rising to the occasion, it's hard to imagine we would leave the fate of the human race to chance. Millions of years of human evolution - everything we've accomplished - wiped out in an instant. And as if to add insult to injury, the only thing preventing us from forestalling our own demise is ourselves.
Meteor Crater, by the way, was created by a 130-foot metallic asteroid some 50,000 years ago. Luckily, the meteorite that hit Chelyabinsk was mostly rock with a bit of iron-nickel, which allowed it to break up more easily and do less damage.
` This is known, of course, because the meteor left a 300-foot trail of over a hundred fragments, with the largest piece, discovered below a large hole in the ice of lake Chebarkul, weighing over two pounds.

Despite this evidence, there are plenty of conspiracy-mongers around Russia who say that the meteor was actually a weapon from the U.S., or perhaps alien activity, or even the hand of God. Dare I take on such mad ideas? Should I even bother?
` There are probably also people who claim to have predicted the impact with psychic powers, but that didn't bother to tell anyone until after the fact. To those folks, I say, either be of use to the world and warn everyone you can, or else stop claiming that you could have done so and didn't.

It is precisely because we can't predict every object that will hit the earth that we just have to sit and wait and hope that we aren't blown up. In the meantime, hope doesn't make a very good bomb shelter, so we're out of luck if caught out in the wrong place at the wrong time.
` Also, if any of you readers wants to join the one or two dozen people whose job it is to track meteoroids, I'll give you a shiny penny. Now, excuse me while I go dig myself a nice bomb shelter...

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